Eye Patches be an iconic symbol of a pirate, yarrr! In the years before advanced medicine and surgery, eyepatches were common for people who had lost an eye. They were particularly prevalent among members of dangerous occupations, such as soldiers and sailors who could lose an eye in battle, as well as blacksmiths who used them to cover one eye for protection from sparks while working.
Telescopes were originally called spyglasses when used for military application, as opposed to astronomy purposes. They became popular after Galileo published his findings on the use of the telescope in March of 1610. Telescopes were constructed by placing a weak concave glass at one end and a strong convex glass at the other end. All navy spyglasses were made of brass to avoid rust.